Various types of communication systems or signal processing systems include a phase locked loop (PLL) for generating a clock signal. PLLs are control systems that generates an output signal having a phase associated with a phase of an input reference signal. In general, PLLs include a phase comparator, a low pass filter (LPF), and a voltage controlled oscillator (VCO). The phase comparator compares the phase of the input reference signal with the phase of a feedback signal fed back from the voltage controlled oscillator, and generates a phase error signal corresponding to a result of the comparison. The LPF removes a high frequency component from the phase error signal to generate a control voltage. The VCO generates the feedback signal having a frequency which is controlled based on the control voltage.